Photographic shutters



' Sept. 3, 1963 E. c. WOODCOCK- 3,102,462

PHOTOGRAPHIC SHUTTERS Original Filed March 24, 1955 2 Sheets-Sheet lfig; l;

INVENTOP Edward Cecl/ Woodcock BY ATTORNEY p 1963 E. C. wooDcocK3,102,462

' PHOTOGRAPHIC SHUTTERS Original Filed March 24, 1955 2 Sheets-Sheet i2lNl/E/VTQP Edward Gee/7 Woodcock BY flaw A 7'7'OPNEV United StatesPatent The present invention relates to photographic shutters andespecially to crank mechanism for operating such shutters of the kindcomprising a spring which is wound up to drive the crank and anes-capement'which permits the crank to rotate through half a revolutionat a time.

The crank is therefore brought suddenly to rest and in the case of ashutter working at high speed while having a large aperture, it isbrought very violently to rest. The terms high speed and large aperture,are, of course relative, but to give an example the actuation of ashutter to give an exposure down to 4 second and controlling an apertureof 1% inch diameter represents the sort of values which arecontemplated.

The present invention consists in the provision of a braking mechanismwhich comes into operation after the crank has been released, but beforeit comes to rest. With an escapement inthe form of an escape toothrotating with the crank and a rocking escapernent lever having twoabutments coasting with the escape tooth, the braking mechanism may beconstituted by a part circular projection extending rearwardly of thetooth, and a braking surface adjacent each abutment on the lever whichcoacts with the part circular projection to brake the movement of thecrank before it comes to rest.

Another problem presented by high speed shutters is the bringing of theobturating members of the shutter itself to rest without-undue shock dueto inertia loads. To deal withthis problem according to the inventionthe mechanism by which the movement of the obturating mechanism isconveyed from the energy source includes a coupling which when the loadexceeds a predetermined value releases but also applies a substantialresistance to relative motion of the two parts. Thus, when the side ofthe coupling which is attached to the energy source is brought to restthe ob-turating members can continue in movement until brought to restby the resistance opposing the resulting relative motion of the twoparts of the coupling. The resistance could be provided by a dashpot orlike fluid controlled device, but it is usually difiicult to accommodatemeans giving a resistance of this kind and instead a frictionalresistance may be employed. v

A particular construction comprises a pin forming one part of thecoupling and an apertured link forming the other part, the aperture.being extended by a slot of slightly smaller width than the diameter ofthe pin and the sides of the link where it is slotted being sufficientlyresilient to enable the pin to spread the sides of the link and movealong the slot; to avoid excessive stresses when the pin first entersthe slot, the slot may be continued from the opposite side of theaperture to that beyond which the pin moves. This extension on "theopposite side can, of course, be narrower than the slot into which thepin moves and at its remote end it may terminate in a circular hole toreduce the risk of fatigue cracks. To keepwear at low value, the pin andlink may be of hardened steel. p

Sucha link can conveniently be used in a shutter of the type in whichsuccessive movements of the link in opposite directions producedsuccessive exposures. In that case, the slot along which the pin movesmay have a full diameter aperture at each end and this full diameteraperture may be continued on the other side by a narrow slot to avoidexcessive stresses as above described. A shutter having blades with aplanetary mounting as described in my application Serial No. 496,3 83,.filed March 24, 1955, now Patent No. 2,916,979, for PhotographicShutters can easily be arranged so that the blades rock in oppositedirections alternately at each successive exposure. In itself, a shutterso arranged is well known and merely requires a form of blade which witha single aperture has a portion on each side of the aperture wide enoughto obtunate the aperture or the appropriate part of the aperture whichthe shutter controls. This type of shutter is usually used close to thecamera lens, generally within the lens as near as possible to thelocation of the stop as the aperture here is the smallest anywhere inthe whole optical system from the object to the image.

When this feature of the invention is applied to a shutter in whichsuccessive exposures are eifected by alternate movement of the link inopposite directions as by successive half revolutions of a crank theconnecting rod may then constitute the link with an aperture at each endof the slot. The parts should be so proportioned that the pin justtravels from one'aperture to the other at the highest shutter speeds.Then at lower speeds it may not travel the whole way, but this is notimportant if the parts are so proportioned that the shutter will closeeven if the pin does not leave the aperture at all.

Such a crank mechanism is commonly actuated by winding up a springwhich'drives the crank and controlling the crank by an escapement whichpermits it to rotate through half a revolution at a time. i

A still further development is concerned with the winding of the springin a mechanism of this kind. It is difficult to arrange such a spring tocover a large range of exposure. To make better provision, the inventionmakes use of two springs in parallel, one comparatively light for lowspeeds and the other comparatively heavy for high speeds. The lightspring is always in action but a predetermined amount of lost motion isprovided in the winding of the heavy spring e.g. a slot covering say inwhich one end of the spring is movable. Thus in winding up from acondition of no tension, winding of the light spring starts at once,while winding of the heavy spring does not start until the lost motionhas been taken up. During any further winding both springs are wound uptogether.

The invention will be further described with reference to theaccompanying drawings which illustrate an example.

FIGURE 1 is an elevation with some parts in section, ofmechanism-according to the present invention,

FIGURE 2 is an elevation partly in section on the line IIII of FIGURE 1,

FIGURE 3 is .aplan taken partly in section on the line Ill-lll of FIGURE1,

FIGURE 4 is an underneath plan View of part of a shutter operated bymechanism according to the present invention, and

FIGURE 5 is a detail of part of FIGURE 4.

The shutter operating mechanism illustrated includes a crank 42 rotatedhalf a revolution at a time.

The mechanism for rotating the crank includes a shaft 46 carrying thecrank, to which a spring load is applied and carrying an escape tooth 47 with which coact abutments 48, 49 on a rocking lever 51. In principlesuch an escape-merit is well known. In FIGURE 3 the tooth .47 is checkedby the abutment 48, and the next movement of the lever will beclockwise, thus releasing the tooth 47 which rotates counterclockwiseand will then be checked by the abutment 49. To lessen the blow oflittle before the tooth engages the abutment.

snoaeea 3 the tooth against the abutment, behind the tooth is provided asurface 52 concentric with the shaft 46, and the lever 51 has twocorresponding braking surfaces 53, 5'4. Thus, at the next step from theposition shown in FIG- URE 3 before the tooth 47 reaches the abutment49, the

surface 52 will come into engagement with the surface 54, thus' brakingthe movement of the rotating parts a The same will happen on the nextmovement when the surface 52 will engage the surface 53. To enable theprecise degree of braking to be adjusted, the lever 51 is split and thetwo parts can be drawn together by a screw 55.

At slow shutter speeds the braking action may bring the crank to restbefore the tooth 47 reaches the next abutment but owing to therelatively small length of the braking surfaces 53, 54, provided theusual dimensional relationships are .m aint-ained in the shuttermechanism there is no risk of the crank coming to rest before theshutter has closed. Nor will there be any interference wi h. the properaction at the next exposure because the very first succeeding movementof the rocking lever 51 will disengage that brake which is in action andthe shafit 46 will immediately rotate until the tooth 47 engages theadjacent abutment before the lever has moved far enough to move thisabutment out of the way of the tooth 47.

In the illustrated example the lever 51 is "carried by a shaftjournalled by rubber bushes and is rocked by the aid of a roller 56working in a cam groove 57 termed in a wheel 58 which is part of themechanism for winding the spring as will be explained below so that aslong as the mechanism is in operation the spring is wound up and theshutter actuated at each half revolution of the wheel 58. -It will beunderstood however that the invention is not limited in this way andthat where preferred the lever 51 may be rocked by any other convenientcontrol "arranged to stop the winding-up movement when the parts areready for the next'exposure. Thus at the termination of each windingoperation a contact may be opened which stops the winding motor orpreferably deenergises an electromagnetic clutch by which the windingmotor is coupled to the Winding mechanism and then whenthe shutter isreleased by operation of the lever 51 the movement of the parts mayclose the contact thus causing the spring to be wound'again.

The spring loading of the shaft 46 is here arranged to enable a widevariation of load, and therefore a wide variation of exposure to beeffected. To this end two springs 59, 61, in parallel are used, seeFIGURE 2, the spring 59 being a light spring and serving for low speedsand the spring 61 a heavy spring serving for high speeds. One end of thespring59 is coupled to a rotatable sleeve 62 and the other end to asleeve 63 fast on the shaft 46. Thus all relative rotation in thewinding up direction between the sleeves 62 and 6.3 winds up the lightspring 59 One end of the spring 61 lies in a cut-away part of the sleeve62 so that it can freely rotate through 180 in relation to this sleevewhile the other end is anchored to the sleeve 63; Thus starting fromaposition in which the spring 61 is under no load and its one end is atthe leading end oftthe cut-away the two sleeves are rotated relativelyin the winding up direction through 180 before any winding up of thespring 61 takes place, in other words the heavy spring 61 is coupledwith lost motion between the sleeve 62 which is part of the windingmeans, and the shaft 46 to which the sleeve 63 is fast, and this lostmotion of 180 has to be taken up before the winding up of the heavyspring 61 commences.

The winding of the springs is efiected from an electric motor 64, whichthrough worm- :gearing 65, and a pinion 66, rotates the wheel 58 withwhich is integral a bevel wheel 67. With the bevel wheel 67 mesh twofurther bevel wheels 68 borne on a spider 69, and with which meshesanother bevel wheel 71 integral with a gear 4 wheel '72 which through anidler wheel 73 rotates the sleeve 62 which has gear teeth formed in itsperipery.

Mani'festly a drive will only be transmitted through the bevel gearingif the spider 69 remains stationary or under control. To this end thespider has hast to it a gear whee-l 74 which can be held stationary orrotated by a train of gearing 75 and two stages of worm gearing 76, 77driven by an electric motor 73. When the motor 78 is stationary the wormgears 76, 77 lock the whole train while when the motor is rotatedadditional move ments can be imparted to the wheel 72 beyond thatimparted through the wheel 58. Thus by means of the motor 7 8 any degreeof preloading can be applied to the springs while when the motor 78 isstationary, the action of the rest of the mechanism is to wind thespring up half a turn for each release of theshutter. It will beunderstood that starting drom a position of no tension on the spring thefirst half revolution will only tension the light spring 59 whileanything beyond half a revolution will tension both springs. Auxiliarygearing 79 is actuated from the wheel 74 to cooperate with remoteindicating or controlling means such as a balanced potentiometer systemso that the load applied to the springs can be indicated or controlledat a distance. r The shutter itself must be of a type which can beactuated by the alternate movements which can be derived from the halfrevolution of the crank 42. Various such The crank 42 is coupled by alink 24 to the pin 23 and at each half revolution of the crank,the pinis thereby moved through a distance adequate to open and reclose theshutter with sufiicient margin to insure the reclosing even if at lowspeed-s the crank comes to rest before the tooth 47 reaches the nextabutment 48 or 49 as above mentioned. The pin 23 engages in a slot 43 inthe link (see FIGURE 5), this slot havingtwo end portions of the samediameter as the pin 23 joined by apart of somewhat less width, and thispart of the 'link is made resilient by two further slots 44 terminatingin round holes 45 to reduce the likelihood of fatigue cracks beingstarted. From the position shown in FIGURE 4 in which the pin 23 is atthe lower end of the'slot 43, the next half revolu tion of the crank 52will carry the pin 23 upwards. At the end of the movement, the movingparts of the shutter will still have considerable kinetic energy due totheir inertia and the pin 23 will spring the sides of the slot 43 apartand move towards the other end of the slot. The parts should be soproportioned thatfthe pin will reach the other end of the slot at aspeed approaching the,

tion. The resilient pressure of the sides of the slot on the pin 23constitute a friction brake which dumps down the movement and thusavoids excessive shock when the shuttercloses. p

This application is a divisional application of United Statesapplication Serial No. 496,3 83,'fi-led March 24, 1955, now Patent No.2,916,979, for Photographic Shutters.

Iclaim: r

1. Mechanism for operating a photographic shutter comprising a crank, aspring for driving the crank, means for winding up the spring betweensuccessive half revolutions of the crank, an escape tooth rotating withthe crank, a rocking escapement lever having two abutments coaoting withthe escape tooththereby to allow the crank to rotate through half arevolution each time the lever is rocked iromone end position to theother, a part circular project-ion concentric with the axis of the crankand extending rearwardly of the tooth, and two braking surfaces adjacentthe abutments :on the lever respectively located to contact the partcircular projection to brake the movement of the crank before it comesto rest against either abutment.

2. Means for opening and closing a photographic shutter including anenergy source for operating the shutter, and a coupling between theenergy source and the shutter, said coupling comprising a pin formingone part of the coupling and an apertured link in which said pin engagesforming the other part of the coupling, the aperture being extended by aslot of slightly smaller width than the transverse dimension of the pinand'the sides of the link where it is slotted being suflicientlyresilient to enable the pin to spread the sides or the link and movealong the slot under the friction due to the resilience of the sides ofthe link. r

3. Means as set forth in claim 2 wherein said aperture is extended onthe opposite side to said slot by another narrow slot to increase theresilience of the link.

4. Means for opening and closing a photographic shutter in which theoperative pants move in opposite directions at successive operationscomprising an energy source for operating the shutter, and a couplingbetween the energy source and the shutter consisting of a pin and a linkhaving a pair of apertures to fit said pin, said link having a slot ofslightly smaller width than the transverse dimension of the pin joiningsaid apertures,-the sides of the link where it is slotted beingsufficiently resilient to enable the pin to spread the sides of the linkand move along the slot from one aperture to the other I der thefriction due to the resilience of the sides of the link.

5. Operating mechanism for a photographic shutter comprising a shaft,means tor permitting said shaft to rotate through a predetermined anglecorresponding to one operation of the shutter, a light spring and aheavy spring, spring winding means, said light spring having one endcoupled to said shaft and the other end coupled to said winding means sothat all relative rotation in the winding up direction between thewinding means and the shaft winds up said light spring, said heavyspring being coupled with lost motion between said winding means andsaid shaft so that relative rotation in the winding up direction betweensaid winding means and said shaft does not commence to wind up saidheavy spring until the lost motion has been taken up.

6. Operating mechanism as set forth in claim 5 wherein one endof saidheavy spring cooperates with a sleeve having a cutaway extending over180 to provide the lost motion.

7. Crank mechanism for operating a photographic shutter of the kindcomprising a spring which is wound up to drive the crank, an escapementwhich permits the crank to rotate through halt a revolution at a time,and a coupling between the crank and the shutter, said mechanisnr alsoincluding a braking mechanism acting upon the crank which comes intooperation each time after the crank has been released but before itcomes to rest, a

coupling between the crank and shutter, means which holds the couplingin action only as long as the load remains below a predetermined valueso that when the load exceeds that value the shutter can continue movingwhen the crank has come to rest, and means which applies a substantialbraking resistance to such continued movement.

8. Crank mechanism for operating a photographic shutter of the kindcomprising a spring which is wound up to drive the crank, an escapementwhich permits the crank to rotate through half a revolution at a time, abraking mechanism which comes into operation each time after the crankhas been released but before it comes to rest, and a coupling betweenthe crank and shutter wherein said coupling comprises a pin and a linkhaving a of spaced apertures tofit said pin, said link having a s-lotofslightly smaller width than the trans-verse dimension of the pin joiningsaid apertures, the sides of the link Where it is slotted beingsufliciently resilient to enable the pin to spread the sides of the linkand move along the slot from one aperture to the other under thefriction due to the resilience of the sides of the link.

9. Crank mechanism as set forth in claim 8 in which the spring which iswound up includes a light spring and a heavy spring and alost motionconnection between the two arranged so that winding of the light springcommences at once but winding of the heavy spring does not commenceuntil the lost motion been taken up.

10. Operating mechanism for a photographic shutter comprising a shaft,control means which at each operation releases said shaft to rotate inone direction through a predetermined angle corresponding to oneoperation of the shutter, spring Winding means including a sleevecoaxial with'the shaft, a light spring coupled at one end to said shaftand at the other end to said sleeve so that all relative rotation of thewinding means in the same direction as said shaft rotates winds up saidlight spring, a driving surtace on said sleeve formed at the trailingend or a cut-away of substantial angular length of the sleeve and aheavy spring anchored at one end to the shaft and having its other endprojecting into said cutaway into the path of said driving surface sothat starting from a position in which the last mentioned end of theheavy spring is at the leading end of the cutaway, winding up of thesleeve spring does not commence until relative rotation of said sleevein the direction in which the shaft rotates through an angle equal tothe length of the cutaway has taken place whereupon said driving surfaceengages said other end of the heavy spring and upon any further relativerotation of the sleeve the heavy spring is wound up.

l1. Operating mechanism as set forth in claim 10 includingmeans forrotating said sleeve through a desired angle while the remainder of themechanism remains stationary thereby imposing a desired pre-load on atleast the light spring, and means for thereafter rotating the sleevethrough said predetermined angle prior to each operation of said controlmeans.

References Cited in the file of this patent UNITED STATES PATENTS2,198,729 Junghans Apr. 30, 1940 2,878,735 Willoox Mar. 24, 19592,925,763 Venning Feb. 23, 1960

1. MECHANISM FOR OPERATING A PHOTOGRAPHIC SHUTTER COMPRISING A CRANK, A SPRING FOR DRIVING THE CRANK, MEANS FOR WINDING UP THE SPRING BETWEEN SUCCESSIVE HALF REVOLUTIONS OF THE CRANK, AN ESCAPE TOOTH ROTATING WITH THE CRANK, A ROCKING ESCAPEMENT LEVER HAVING TWO ABUTMENTS COACTING WITH THE ESCAPE TOOTH THEREBY TO ALLOW THE CRANK TO ROTATE THROUGH HALF A REVOLUTION EACH TIME THE LEVER IS ROCKED FROM ONE END POSITION TO THE OTHER, A PART CIRCULAR 